JPS6089605A - Combustion method for fuel oil - Google Patents

Abstract

PURPOSE:To contrive to ensure a combustion system having a high turndown ratio, by a method wherein a fuel oil and a self-burning gas serving as a spray medium are fed to a fuel oil feed cylinder incorporating a mixer, and the self- burning gas is used as assistant combustion for the fuel oil. CONSTITUTION:A mixer 2 consists of a fuel flow pore 5, a self-burning gas flow pore 6, and a mixing chamber 7, and a fuel oil A and a self-burning gas B are fed in the mixing chamber 7 through pores 5 and 6 by means of feed pipes 3 and 4, respectively, to mix them together. The oil-gas mixture fuel is discharged through injection nozzles 8 formed in the forward end of the body of a feed cylinder 1, and in this case, the mixture fuel is injected and sprayed by means of a movement amount of the fuel oil itself for combustion. This causes increasing of an assistant combustion effect on an oil drop 11 by means of the combustion heat of a self-burning gas layer 13 on the outer surface of the oil drop 11 is high, and as a result, a rate is seldom determined by means of an oil drop of size and a relative speed 14 between the oil drop and the atmosphere.

Description

[Detailed description of the invention] The present invention relates to a fuel oil combustion method.

The combustor (burner) installed in tube heating furnaces, boilers, and other combustion furnaces is an important component that controls the performance of the furnace, and for this purpose, the main functions required of the combustor are: (7) Stable combustion can be achieved within the load range according to process requirements, (f) Good flame shape, (1) Less excess air, and (7) In the case of fuel oil combustion, especially fuel oil (3) There is no clogging of fuel oil in the injection hole (burner tip), and (3) there is little generation of NOx (nitrogen oxides).

Here, regarding fuel oil combustors, there are the following three methods as typical conventional combustion methods.

(1) Steam spray method This method is the mainstream of oil combustion and uses steam to atomize the oil. Superheated steam is generally used as the steam, and the amount of steam sprayed is approximately Requires 10-50% by weight, steam pressure is about 1-5) c!
Supplied at a high price of $/cm”.

(11) High-pressure air atomization method Atomizes the oil with air instead of steam (+) above.The amount of air sprayed is 2 to 10 inches of the theoretical combustion air amount, and the air pressure is the same as in (1), which is oil pressure. It is fed approximately 1 to 1/2 mouths higher than the standard.

Sub-hydraulic spraying method This method does not use a spraying medium and atomizes pressurized and heated oil by passing it through small holes.

In this case, the oil pressure needs to be raised to about 5 to 5'Okg/m2G.

However, a common drawback of the conventional typical fuel oil combustion methods described above is the stable combustion range, that is, [minimum combustion amount/maximum combustion amount (Turn Dovrn Ra
tio) ) is as small as about 173 to 1/4.

As a result of research efforts aimed at establishing a combustion method with a higher turndown ratio than conventional methods, the inventors of the present invention have discovered that they can reduce fuel oil by using combustible gas in place of conventional steam or high-pressure or low-pressure air. It was discovered that the stable combustion range can be set to 0 to 100% and the above object can be achieved, leading to the present invention.

That is, the gist of the present invention is to supply fuel oil and a self-combustible gas as an atomizing medium to a fuel oil supply tube incorporating a mixer, and to use the self-combustible gas for auxiliary combustion of the fuel oil. The present invention provides a method for burning fuel oil.

The characteristics of the method of the present invention are as follows when compared with the conventional method.

fl) Combustion mechanism concept Conventional method; Oil droplets are atomized to ensure combustibility. Present invention; combustibility is ensured by the auxiliary combustion effect (assist burning) of self-combustible gas (setting of operating conditions).

(2) Supply pressure of spray medium (maximum combustion) Conventional type: Hydraulic glass 1 kIt/cm" or more Invention: Hydraulic pressure plus 5 kg/cm" or less (3) Type of spray medium Conventional type: Steam, high pressure and low pressure air Invention; flammable gas (4) Burning speed Conventional type: Rapid combustion Invention 1 Slow combustion (5) NO! Reduction effect conventional type; No favorite F! A: ■ Slow combustion in item (4) ■ NOx reduction reaction in the flame due to flammable gas (reducing gas) Reduction effect due to the above ■ and ■ (20% or more reduction compared to conventional type) Self-combustion in the present invention The calorific value (L, H,
V, or Low Heating Value: The net calorific value of the fuel, which is the unit calorific value when burning the fuel @
It refers to the calorific value of shi. Kcal/ Mm” or Kcal/
k? For example, natural gas, hydrocarbon gas such as oil refining off-gas containing H2, OH, etc. can be used as long as it has a NOx reduction effect. Any hydrocarbon gas may be used.

The present invention will be specifically explained below with reference to the drawings.

Figure 1 shows a conventional fuel oil supply tube (oil gun).
This is just an example, and the fuel oil supply tube used in the present invention may have this conventional structure.

The fuel oil supply pipe 1 is made up of a mixer (atomizer) 2, a fuel supply pipe 3, and a self-combustible gas supply pipe 4. (In the conventional system, 4 is used as an atomizing medium supply pipe. is supplied from the respective supply pipes 3 and 4 through the small holes 5 and 6 into the mixing chamber 7 and mixed therein. However, at this time, the momentum of the fuel oil itself causes it to be sprayed out and atomized.
Burn.

The combustion mechanism of the atomized fuel oil section will be explained using FIG. 2, which compares it with a steam spray method, which is an example of a conventional method.

Figure 2 (a) shows the combustion of oil droplets by the conventional method, and the same (
1)) shows the method of the present invention, and 1 in the figure
1 is a single oil droplet, 12 is a combustion surface, 13 is a self-combustible gas layer, and 14 is a relative flow velocity.

In the conventional method shown in FIG. 2(a), the oil droplet 11 is
2. It evaporates and burns due to heat transfer from the high temperature air on the outside.

In contrast, in the method of the present invention shown in FIG. 2('b), a self-combustible gas layer 13 is formed outside the single oil droplet 11. Therefore, the oil droplet 11 evaporates and burns at the same time as the combustion of the self-combustible gas layer 13 occurs due to heat transfer from the outside high-temperature air through the combustion surface 12.

It is important to note here that in the case of the steam atomization method, in order to ensure combustibility, the pressure of the spray steam must be raised above the hydraulic pressure of the fuel oil to atomize the oil droplets, and ■ The air in the combustion chamber must be Two essential conditions are to increase the relative velocity (relative comparison between the flow of combustion gas generated by combustion of fuel in a combustion furnace and the falling or rising velocity of droplets) 14. If the respective flow velocities of fuel and air decrease, the mixing will deteriorate, resulting in poor combustion. If the fuel flow rate is low and the air flow rate is low, it will blow out, and if the air flow rate is too low, incomplete combustion will occur. Therefore, an optimal difference between the flow velocities of fuel and air (that is, an optimal relative velocity) and ensuring a certain absolute flow velocity of both contribute to the stability of combustion.

On the other hand, in the method of the present invention, since the combustion heat of the combustible gas layer 15 on the outer surface of the oil droplet 11 has a large auxiliary combustion effect on the oil droplet 11, the diameter of the oil droplet and the relative relationship with the atmosphere are greater than in the steam spray method. The speed is rarely limited by the speed 14. (
Since the oil spray speed decreases in the low combustion range, the relative velocity inevitably decreases. ) The effects of the present invention compared with the conventional method are as follows.

1) Oil droplet atomization does not need to be as fine as the conventional method,
Therefore, combustion is possible even if the combustible gas pressure is lower than the hydraulic pressure. The preferred gas pressure is combustion oil pressure plus 5 kg/
on2 or less.

Since the relative velocity with the atmosphere can be lower than the conventional method, the stable combustion range of fuel oil is 0 to 100 as long as gas is present.
% can be secured.

111) Fuel oil combustion is a slow combustion due to the combustion of flammable gas, and due to the reduction action of flammable gas. , a reduction reaction of NOX occurs. As described above, there is an effect of reducing J NOx.

Demonstrative data regarding the effects of the above method of the present invention will be specifically shown by citing the results of Example 1 and Comparative Example 1.

1. Example 1 Using the apparatus shown in FIG. 1, combustion was carried out using the following combustion oil and self-combustible gas. Table 1 summarizes each condition and the obtained flame length.

Table 1 Fuel oil properties: Su7? Specific gravity 15/4℃ 0.76 viscosity (
cp) 0.66 Composition (wt%) 0:86. H=14 LHV (Kcal/in?) 10.500 Self-combustible gas; natural gas LHV=9450 Kcal,/radius Here, regarding the excess air ratio, the air conditioning installed in the wind box surrounding the device shown in Figure 1. Adjustments were made by opening and closing the grid.

Further, since the flame length is limited by the size of the furnace body, an abnormally long or short flame will cause uneven heating, making it difficult to maintain performance in a production furnace or the like. The general flame length is 1 to 4.
It is tyt.

In the case of the conventional method, the stable combustion range of normal fuel oil is 50 to 100 degrees as the minimum combustion amount/maximum combustion amount. On the other hand, the method of the present invention has a combustion amount of 6 & 2 in test number 79.
When ky/H is 100%, test number 80 is 0
%, test number 104 was about 11 inches, and it can be seen from Table 1 that the stable combustion range was 0 to 100%, clearly wider than the conventional method.

1 Comparative Experimental Example 1 Using the apparatus shown in FIG. 1, a comparison was made between the method of the present invention using self-combustible gas spraying and the conventional steam spraying method. The conditions and the results obtained are summarized in Table 2.

Table 2 Fuel oil properties; C heavy oil AP engineering Gr Note>(6[]'F) 15.8LHV =
10.800 Kcal/9 self-mass; Natural Is LHV = 9450 KcaVNm' Note AP engineering Gr: American Petroleum engineering n5 titute Gravity From Table 2, the fuel oil pressure of the method of the present invention is 13 kg compared to the conventional steam spray method. 9/cr to 21-2.6 compared to /-
n2G, the pressure of the combustible gas can be much lower than the pressure for atomizing steam, and the NOX level #
(ppm) is also 6%o, converted to 145.159 pp
m and 187.214 ppm for the steam atomization method. That is, the effect of reducing NOX is clearly recognized.

From the data shown in I and (2) above, it is clear that the effect of the method of the present invention, that is, the stable combustion range of fuel oil is wide from 0 to 100%, and that NOx is reduced. Not only can it be applied to a single burner or equipment installed with various types of burners (e.g. boilers, heating furnaces, indirators, incinerators, etc.), but it can also be applied to conventional burners in existing equipment, such as those mentioned above, by simply replacing the mixer. This is a highly practical method that can be easily modified.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of a fuel oil supply cylinder used in the method of the present invention, and FIG.
)) are diagrams each illustrating the oil droplet combustion mechanism of the method of the present invention. Continuing from page 1 @ Inventor Column Yunosuke 35ooI Matsushi, Niigata City Inventor Ken 1) Hidenobu 350 Matsuhama-cho, Niigata City
@ Mitsubishi Gas Chemical Co., Ltd. Niigata Industrial Office Mitsubishi Gas Chemical Co., Ltd. Niigata Industrial Office

Claims (1)

[Claims] A fuel oil combustion method characterized in that fuel oil and a self-combustible gas as an atomizing medium are supplied to a fuel oil supply cylinder having a built-in mixer, and the self-combustible gas is used for auxiliary combustion of the fuel oil.